Approach to Posture and Gait in Huntington's Disease

Subtyping monogenic disorders: Huntington disease

Huntington disease is a highly disabling neurodegenerative disease characterized by psychiatric, cognitive, and motor deficits. The causal genetic mutation in huntingtin (Htt, also known as IT15), located on chromosome 4p16.3, leads to an expansion of a triplet coding for polyglutamine. The expansion is invariably associated with the disease when >39 repeats. Htt encodes for the protein huntingtin (HTT), which carries out many essential biological functions in the cell, in particular in the nervous system. The precise mechanism of toxicity is not known. Based on a one-gene-one-disease framework, the prevailing hypothesis ascribes toxicity to the universal aggregation of HTT. However, the aggregation process into mutant huntingtin (mHTT) is associated with a reduction of the levels of wild-type HTT. A loss of wild-type HTT may plausibly be pathogenic, contributing to the disease onset and progressive neurodegeneration. Moreover, many other biological pathways are altered in Huntington disease, such as in the autophagic system, mitochondria, and essential proteins beyond HTT, potentially explaining biological and clinical differences among affected individuals. As one gene does not mean one disease, future efforts at identifying specific Huntington subtypes are important to design biologically tailored therapeutic approaches that correct the corresponding biological pathways-rather than continuing to exclusively target the common denominator of HTT aggregation for elimination.

Adaptive Inertial Sensor-Based Step Length Estimation Model

Pedestrian dead reckoning (PDR) using inertial sensors has paved the way for developing several approaches to step length estimation. In particular, emerging step length estimation models are readily available to be utilized on smartphones, yet they are seldom formulated considering the kinematics of the human body during walking in combination with measured step lengths. We present a new step length estimation model based on the acceleration magnitude and step frequency inputs herein. Spatial positions of anatomical landmarks on the human body during walking, tracked by an optical measurement system, were utilized in the derivation process. We evaluated the performance of the proposed model using our publicly available dataset that includes measurements collected for two types of walking modes, i.e., walking on a treadmill and rectangular-shaped test polygon. The proposed model achieved an overall mean absolute error (MAE) of 5.64 cm on the treadmill and an overall mean walked distance error of 4.55% on the test polygon, outperforming all the models selected for the comparison. The proposed model was also least affected by walking speed and is unaffected by smartphone orientation. Due to its promising results and favorable characteristics, it could present an appealing alternative for step length estimation in PDR-based approaches.

Health care resource utilization and costs among individuals with vs without Huntington disease in a US population

BACKGROUND: Quantifying the extent of health care resource utilization (HCRU) and costs associated with Huntington disease (HD) is vital for providers, decisionmakers, and payers to understand unmet treatment needs and to ensure limited resources can be used to benefit the maximum number of people with HD. OBJECTIVE: To quantify HCRU and costs for people with HD, overall and by disease stage, and compare these with non-HD controls. METHODS: This was a retrospective cohort study using administrative claims data from the IBM MarketScan Commercial, Multi-State Medicaid, and Medicare Supplemental Databases from January 1, 2009, to December 31, 2018. People with an HD claim between January 1, 2010, and December 31, 2017, were selected for this analysis and matched with non-HD controls for comparison. The HD cohort and the non-HD controls were exact matched on their follow-up duration and propensity score matched 1:4 to create the final analytical cohort. Index date was the first HD diagnosis for the HD cohort (proxy index date assigned to controls), and all individuals were required to have continuous enrollment for 12 or more months pre-index (baseline) and 3 or more months post-index. Proportions of all-cause HCRU (ie, outpatient visits, inpatient visits, emergency department visits, pharmacy fills, radiology visits, and physical/occupational therapy visits) in the 6-months post-index and HCRU counts and costs per patient per month (PPPM) over the entire follow-up were calculated for each cohort. RESULTS: A total of 2,473 individuals with HD and 9,522 matched non-HD controls were identified. HCRU in 6 months post-index was significantly greater in people with HD compared with non-HD controls for all health care service categories; P < 0.0001. The mean number of HCRU PPPM for all measured healthcare services was significantly higher in people with HD compared with non-HD controls (P < 0.001). Mean total costs (2018 USD PPPM) for the HD cohort ($2,260 [SD = $4,682]) were twice the total costs in the non-HD cohort ($1,056 [SD = $3,078]) (P < 0.0001) and were highest across all disease stages. CONCLUSIONS: This study provides current comprehensive HCRU and cost estimates in individuals with HD relative to those without the disease, thus demonstrating the high economic burden imposed by HD. DISCLOSURES: Dr Ta: Employment with Genentech (at time of study) and stock options with Roche; Dr To: Employment and stock options/dividends with Genentech; Dr Patel: Employment and stock options with Roche/Genentech; Dr Fuller: Employment with CHDI Management/CHDI Foundation; Mr Surinach: Employment with Genesis Research (which receives consulting fees from Genentech/Roche); Dr Abbass: Employment and stock options with Genentech; Dr Exuzides: Employment and stock options with Roche/Genentech; and Ms Luo: Employment with CHDI Management/CHDI Foundation. This study was funded by Genentech Inc. The authors thank Greg Rowe of Chrysalis Medical Communications for providing medical writing support, which was funded by F. Hoffmann-La Roche Ltd, in accordance with Good Publication Practice (GPP3) guidelines (http://www.ismpp.org/gpp3).

Measuring Movement in Health and Disease

Evaluating and quantifying the many aspects of movement -- from open-field locomotion and stepping patterns in rodent models to stride trajectory and postural sway in human patients -- are key to understanding brain function. Various experimental approaches have been used in applying these lines of research to investigate the brain mechanisms underlying neurodegenerative disease. Although valuable, data on movement are often limited by the shortcomings inherent in the data collection process itself. Steve Fowler and his research group have been instrumental in pioneering a technology that both minimizes these pitfalls in studies of rodent behavior and has applications to research on human patients. At the center of this technology is the force-plate actometer, developed by the Fowler group to assess multiple aspects of movement in rodent models. Our review highlights how use of the actometer and related behavioral measurements provides valuable insight into Huntington's disease (HD), an autosomal dominant condition of progressively deteriorating behavioral control. HD typically emerges in mid-life and has been replicated in multiple genetically engineered mouse models. The actometer also can be a valuable addition to cutting-edge neuronal and synaptic technologies that are now increasingly applied to studies of behaving animals. In short, the impact of the Fowler contribution to the neuroscience of movement is both meaningful and ongoing.